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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
8174f150 MH |
2 | /* |
3 | * kernel/freezer.c - Function to freeze a process | |
4 | * | |
5 | * Originally from kernel/power/process.c | |
6 | */ | |
7 | ||
8 | #include <linux/interrupt.h> | |
9 | #include <linux/suspend.h> | |
9984de1a | 10 | #include <linux/export.h> |
8174f150 MH |
11 | #include <linux/syscalls.h> |
12 | #include <linux/freezer.h> | |
8a32c441 | 13 | #include <linux/kthread.h> |
8174f150 | 14 | |
a3201227 TH |
15 | /* total number of freezing conditions in effect */ |
16 | atomic_t system_freezing_cnt = ATOMIC_INIT(0); | |
17 | EXPORT_SYMBOL(system_freezing_cnt); | |
18 | ||
55f2503c PL |
19 | /* indicate whether PM freezing is in effect, protected by |
20 | * system_transition_mutex | |
21 | */ | |
a3201227 TH |
22 | bool pm_freezing; |
23 | bool pm_nosig_freezing; | |
24 | ||
85fbd722 TH |
25 | /* |
26 | * Temporary export for the deadlock workaround in ata_scsi_hotplug(). | |
27 | * Remove once the hack becomes unnecessary. | |
28 | */ | |
29 | EXPORT_SYMBOL_GPL(pm_freezing); | |
30 | ||
0c9af092 TH |
31 | /* protects freezing and frozen transitions */ |
32 | static DEFINE_SPINLOCK(freezer_lock); | |
8174f150 | 33 | |
a3201227 TH |
34 | /** |
35 | * freezing_slow_path - slow path for testing whether a task needs to be frozen | |
36 | * @p: task to be tested | |
37 | * | |
38 | * This function is called by freezing() if system_freezing_cnt isn't zero | |
39 | * and tests whether @p needs to enter and stay in frozen state. Can be | |
40 | * called under any context. The freezers are responsible for ensuring the | |
41 | * target tasks see the updated state. | |
42 | */ | |
43 | bool freezing_slow_path(struct task_struct *p) | |
44 | { | |
2b44c4db | 45 | if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK)) |
a3201227 TH |
46 | return false; |
47 | ||
a34c80a7 | 48 | if (test_tsk_thread_flag(p, TIF_MEMDIE)) |
51fae6da CW |
49 | return false; |
50 | ||
a3201227 TH |
51 | if (pm_nosig_freezing || cgroup_freezing(p)) |
52 | return true; | |
53 | ||
34b087e4 | 54 | if (pm_freezing && !(p->flags & PF_KTHREAD)) |
a3201227 TH |
55 | return true; |
56 | ||
57 | return false; | |
58 | } | |
59 | EXPORT_SYMBOL(freezing_slow_path); | |
60 | ||
8174f150 | 61 | /* Refrigerator is place where frozen processes are stored :-). */ |
8a32c441 | 62 | bool __refrigerator(bool check_kthr_stop) |
8174f150 MH |
63 | { |
64 | /* Hmm, should we be allowed to suspend when there are realtime | |
65 | processes around? */ | |
a0acae0e | 66 | bool was_frozen = false; |
5ece3eae | 67 | long save = current->state; |
8174f150 | 68 | |
8174f150 MH |
69 | pr_debug("%s entered refrigerator\n", current->comm); |
70 | ||
8174f150 MH |
71 | for (;;) { |
72 | set_current_state(TASK_UNINTERRUPTIBLE); | |
5ece3eae TH |
73 | |
74 | spin_lock_irq(&freezer_lock); | |
75 | current->flags |= PF_FROZEN; | |
6907483b | 76 | if (!freezing(current) || |
8a32c441 | 77 | (check_kthr_stop && kthread_should_stop())) |
5ece3eae TH |
78 | current->flags &= ~PF_FROZEN; |
79 | spin_unlock_irq(&freezer_lock); | |
80 | ||
81 | if (!(current->flags & PF_FROZEN)) | |
8174f150 | 82 | break; |
a0acae0e | 83 | was_frozen = true; |
8174f150 MH |
84 | schedule(); |
85 | } | |
6301cb95 | 86 | |
8174f150 | 87 | pr_debug("%s left refrigerator\n", current->comm); |
50fb4f7f TH |
88 | |
89 | /* | |
90 | * Restore saved task state before returning. The mb'd version | |
91 | * needs to be used; otherwise, it might silently break | |
92 | * synchronization which depends on ordered task state change. | |
93 | */ | |
94 | set_current_state(save); | |
a0acae0e TH |
95 | |
96 | return was_frozen; | |
8174f150 | 97 | } |
a0acae0e | 98 | EXPORT_SYMBOL(__refrigerator); |
8174f150 MH |
99 | |
100 | static void fake_signal_wake_up(struct task_struct *p) | |
101 | { | |
102 | unsigned long flags; | |
103 | ||
37ad8aca TH |
104 | if (lock_task_sighand(p, &flags)) { |
105 | signal_wake_up(p, 0); | |
106 | unlock_task_sighand(p, &flags); | |
107 | } | |
8174f150 MH |
108 | } |
109 | ||
110 | /** | |
839e3407 TH |
111 | * freeze_task - send a freeze request to given task |
112 | * @p: task to send the request to | |
8174f150 | 113 | * |
37f08be1 MPS |
114 | * If @p is freezing, the freeze request is sent either by sending a fake |
115 | * signal (if it's not a kernel thread) or waking it up (if it's a kernel | |
116 | * thread). | |
839e3407 TH |
117 | * |
118 | * RETURNS: | |
119 | * %false, if @p is not freezing or already frozen; %true, otherwise | |
8174f150 | 120 | */ |
839e3407 | 121 | bool freeze_task(struct task_struct *p) |
8174f150 | 122 | { |
0c9af092 | 123 | unsigned long flags; |
0c9af092 | 124 | |
613f5d13 CC |
125 | /* |
126 | * This check can race with freezer_do_not_count, but worst case that | |
127 | * will result in an extra wakeup being sent to the task. It does not | |
128 | * race with freezer_count(), the barriers in freezer_count() and | |
129 | * freezer_should_skip() ensure that either freezer_count() sees | |
130 | * freezing == true in try_to_freeze() and freezes, or | |
131 | * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task | |
132 | * normally. | |
133 | */ | |
134 | if (freezer_should_skip(p)) | |
135 | return false; | |
136 | ||
0c9af092 | 137 | spin_lock_irqsave(&freezer_lock, flags); |
a3201227 TH |
138 | if (!freezing(p) || frozen(p)) { |
139 | spin_unlock_irqrestore(&freezer_lock, flags); | |
140 | return false; | |
141 | } | |
8174f150 | 142 | |
5d8f72b5 | 143 | if (!(p->flags & PF_KTHREAD)) |
8cfe400c | 144 | fake_signal_wake_up(p); |
5d8f72b5 | 145 | else |
8174f150 | 146 | wake_up_state(p, TASK_INTERRUPTIBLE); |
a3201227 | 147 | |
0c9af092 | 148 | spin_unlock_irqrestore(&freezer_lock, flags); |
a3201227 | 149 | return true; |
8174f150 MH |
150 | } |
151 | ||
a5be2d0d | 152 | void __thaw_task(struct task_struct *p) |
dc52ddc0 | 153 | { |
0c9af092 | 154 | unsigned long flags; |
a5be2d0d | 155 | |
0c9af092 | 156 | spin_lock_irqsave(&freezer_lock, flags); |
34b087e4 | 157 | if (frozen(p)) |
a5be2d0d | 158 | wake_up_process(p); |
0c9af092 | 159 | spin_unlock_irqrestore(&freezer_lock, flags); |
dc52ddc0 | 160 | } |
96ee6d85 TH |
161 | |
162 | /** | |
34b087e4 | 163 | * set_freezable - make %current freezable |
96ee6d85 TH |
164 | * |
165 | * Mark %current freezable and enter refrigerator if necessary. | |
166 | */ | |
34b087e4 | 167 | bool set_freezable(void) |
96ee6d85 TH |
168 | { |
169 | might_sleep(); | |
170 | ||
171 | /* | |
172 | * Modify flags while holding freezer_lock. This ensures the | |
173 | * freezer notices that we aren't frozen yet or the freezing | |
174 | * condition is visible to try_to_freeze() below. | |
175 | */ | |
176 | spin_lock_irq(&freezer_lock); | |
177 | current->flags &= ~PF_NOFREEZE; | |
96ee6d85 TH |
178 | spin_unlock_irq(&freezer_lock); |
179 | ||
180 | return try_to_freeze(); | |
181 | } | |
34b087e4 | 182 | EXPORT_SYMBOL(set_freezable); |